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University
of Rhode Island GreenShare Factsheets
Poinsettias
The poinsettia (Euphorbia pulcherrima), one of
the most popular winter holiday plants, is a native to the
area around Taxco, Mexico. Joel R. Poinsett, the first United
States ambassador to Mexico, introduced it into the United
States. In Mexico, poinsettias grow to be large woody shrubs,
often reaching heights above 10 feet.
Poinsettia is a member of the spurge family and is characterized
by small, inconspicuous flowers (cyathia) and large, brightly
colored, leaf-like bracts. Poinsettia bracts may be red, pink,
white, yellow, speckled or marbled; the most popular color
is red.
Poinsettias are often thought of as poisonous, but research
indicates that poinsettias contain no chemicals commonly considered
toxic; however, eating the plants is not recommended. While
most people are not sensitive to the sap, it can cause a mild
skin irritation.
• Place the plant where
it will receive a maximum amount of indoor sunlight.
• Premature leaf drop
is one of the main problems in poinsettia care. The plant
needs to be kept out of drafts,
as rapid temperature fluctuations will cause premature leaf
drop. Even touching a cold windowpane can cause injury to the
bracts. Night temperatures should be no cooler than 60 to 65
degrees F. Day temperatures should not exceed 80 degrees F.
• Another cause of leaf
drop is wilting. The soil must be kept slightly moist but
not soggy. Water thoroughly
and make sure the pot has good drainage. Empty out any water
that may be left in the pot saucer after watering.
• Fertilization is typically
not needed for the first month because the potting mix includes
a slow-release
fertilizer. After the first month, fertilize once every two
weeks until the plant loses its brightly colored bracts.
• Always remove any
paper or plastic sleeve. Ethylene gas can accumulate within
the sleeve and cause premature
flower drop and leaf curling.
• Many of the new poinsettia
cultivars will keep their leaves and remain attractive even
in summer.
If the plant retains its leaves, treat it like any houseplant.
Place it in a sunny location and apply a complete fertilizer
containing trace elements once every two weeks. As soon as
night temperatures reach a minimum of 60 degrees F, the plant
can be set outside.
Once a poinsettia plant drops its leaves, let the soil
dry out and keep the plant in a cool location--it still needs
some light. The temperature should not rise above 60 degrees
F; between 50 and 55 degrees F is ideal. In late April or early
May, bring the plant out of its resting stage. Cut the stems
back to about 3 to 8 inches above the soil. If there is more
than one plant per pot, separate them and replant in individual
containers.
If repotting is necessary, use a soil mix that is loose
and porous. A soil mixture composed of three parts sterilized
soil, two parts organic matter (peat or sterile compost) and
one part perlite or vermiculite works well. You also can buy
a premixed, pasteurized media. If you are mixing your own soil,
add one teaspoon of superphosphate or bone meal for every 2
1/2 cups of soil mixture and thoroughly mix in.
Place the plant in a light, warm
place and water whenever the soil begins to dry. As soon
as the night temperature
reaches a minimum of 60 degrees F, the plant can be set outside.
Place the plant in a shady location for two to three weeks
to allow for acclimatization and to prevent leaf sun scald,
then sink the pot in a sunny location with well-drained soil.
Give the pot 1/4 turn every few weeks to break off any roots
that might be growing through the drainage holes.
Once the new shoots are about 1
inch long, apply a complete fertilizer containing trace elements.
Use either a water-soluble
fertilizer or a slow-release fertilizer -- follow label directions.
Fertilize plants at seven to ten day intervals. To
prevent your poinsettia from getting too tall, pinch off or
prune the growing tips when they are about 4-6 inches long.
If the new shoots grow another 5 inches before late August,
repeat the process. Pruning shapes the plant to form an attractive
compact growth.
Poinsettias are short-day plants, which means they flower
about 10 weeks after the daylight shortens to 12 hours or less.
For Christmas bloom, the plant must be kept in full darkness
between 5 p.m. and 8 a.m. from early October until late November.
Flowering will be delayed if there is any exposure to light
during those hours. The plant can be put in a sunny window
during the day hours. Fertilizing should continue until mid-December.
Several insects may attack poinsettias:
white flies, fungus gnats, mealybugs and spider mites. The
adult white
fly looks like a small fly covered with white powder. Fungus
gnats are small, dark-colored flies about 3 mm (1/8 inch) long.
They can be found either on the plant or soil surface. The
adults are more of a nuisance than a real problem, but the
larvae do feed on plant tissue. Mealybugs are
serious pests of poinsettias. These insects are soft-bodied
and appear as a cottony mass, usually in the axis of the leaves. Gently
cleaning the leaves with alcohol on a swab can control mealybugs,
aphids and spider mites if caught early. Other choices for
control are a variety of sprays. Read the labels carefully
before using.
Most serious diseases that affect poinsettias are soil-borne
and are primarily fungi. The easiest methods for controlling
these disease organisms are by sanitation and periodic use
of a fungicide.
If you want to propagate poinsettia, take leafy cuttings
during early to mid-August. Cuttings should be about 4 inches
long and may be rooted in any pasteurized media. The use of
rooting compounds will increase the percentage of cuttings
that will root and the rate of rooting. Place the pots where
humidity is high. A terrarium or similar structure with high
humidity is an ideal location for raising poinsettias. The
leaves on the cuttings should not wilt. To prevent this, reduce
the amount of leafy surface by cutting some basal leaves in
half--shading the cuttings. The more light the cuttings can
be exposed to without wilting, the more rapidly the rooting
and the more vigorous the rooted cutting. Keep the medium moist
but not saturated with water. Air temperature of about 70 degrees
F by day and 60 degrees F by night is best for rooting. Cuttings
will root in about three to four weeks. Further treatment of
the rooted cuttings is the same as for plants bought from commercial
sources.
Adapted from a fact sheet
published by University of Nebraska Cooperative Extension,
Institute of Agriculture and Natural Resources. Authors Jay
B. Fitzgerald and Donald H. Steinegger.
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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